The invention relates to the field of refractory materials mechanically reinforced by the addition of fibers.
Traditional refractories made up of metal oxides and/or carbon have very limited mechanical properties. For certain applications, it has been shown that the lifetime of a refractory lining depends more on its mechanical properties than on its intrinsic refractory qualities. For example, it is the case for the lining of pouring ladles, and particularly the top part of the ladle referred to as the spout which is the seat of continuous clogging up under the effect of the progressive solidification of the products being cast. Because of this, it is subjected to scouring operations at regular intervals. This scouring is accompanied inevitably by the removal of the refractory lining when the deposits to be removed stick, to a greater or lesser degree, to the refractory. This is practically always the case.
It is known that, on a pouring spout made of graphite, the deposits stick rather less but exposure of the graphite to the air limits its lifetime due to oxidation. Furthermore it is a material which is a relatively good thermal conductor, which favors deposition and clogging.
According to the current state of the technology, the best results with respect to lifetime are obtained by using castable refractories filled with metal fibers.
The aim of the invention is to provide refractory materials reinforced by fibers and made stronger by the use of fibers which are more suitable than the metal fibers of the prior art.
The subject of the invention is fibers for the reinforcement of refractory materials constituted by sintered bauxite having a length/diameter ratio which is greater than 10. These fibers have a cylindrical or prismatic form truncated by two surfaces, for example, surfaces that are substantially planar and perpendicular to the axis of the cylinder or prism. The prismatic shapes may have a section comprising concave areas, for example in the form of a star. For fibers of circular section, the diameter is that of the circle of the section. For other section shapes, the diameter is that of the circle having the same surface area as the section (an equivalent diameter).
Another subject of the invention is a castable refractory based on metal oxides reinforced by the incorporation of from 0.1 to 50% by weight of fibers of sintered bauxite such as those described below.